Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit d4f7a2c1 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Andi Kleen
Browse files

[PATCH] i386: Relocate VDSO ELF headers to match mapped location with COMPAT_VDSO 



Some versions of libc can't deal with a VDSO which doesn't have its
ELF headers matching its mapped address.  COMPAT_VDSO maps the VDSO at
a specific system-wide fixed address.  Previously this was all done at
build time, on the grounds that the fixed VDSO address is always at
the top of the address space.  However, a hypervisor may reserve some
of that address space, pushing the fixmap address down.

This patch does the adjustment dynamically at runtime, depending on
the runtime location of the VDSO fixmap.

[ Patch has been through several hands: Jan Beulich wrote the orignal
  version; Zach reworked it, and Jeremy converted it to relocate phdrs
  as well as sections. ]

Signed-off-by: default avatarJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Cc: Zachary Amsden <zach@vmware.com>
Cc: "Jan Beulich" <JBeulich@novell.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Roland McGrath <roland@redhat.com>
parent a6c4e076

arch/i386/kernel/entry.S

+0 −4
Original line number Diff line number Diff line
@@ -305,16 +305,12 @@ sysenter_past_esp: 
	pushl $(__USER_CS)

	CFI_ADJUST_CFA_OFFSET 4

	/*CFI_REL_OFFSET cs, 0*/

#ifndef CONFIG_COMPAT_VDSO

	/*

	 * Push current_thread_info()->sysenter_return to the stack.

	 * A tiny bit of offset fixup is necessary - 4*4 means the 4 words

	 * pushed above; +8 corresponds to copy_thread's esp0 setting.

	 */

	pushl (TI_sysenter_return-THREAD_SIZE+8+4*4)(%esp)

#else

	pushl $SYSENTER_RETURN

#endif

	CFI_ADJUST_CFA_OFFSET 4

	CFI_REL_OFFSET eip, 0

arch/i386/kernel/sysenter.c

+149 −9
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <asm/msr.h>

#include <asm/pgtable.h>

#include <asm/unistd.h>

#include <asm/elf.h>



/*

 * Should the kernel map a VDSO page into processes and pass its
@@ -46,6 +47,129 @@ __setup("vdso=", vdso_setup); 


extern asmlinkage void sysenter_entry(void);



#ifdef CONFIG_COMPAT_VDSO

static __init void reloc_symtab(Elf32_Ehdr *ehdr,

				unsigned offset, unsigned size)

{

	Elf32_Sym *sym = (void *)ehdr + offset;

	unsigned nsym = size / sizeof(*sym);

	unsigned i;



	for(i = 0; i < nsym; i++, sym++) {

		if (sym->st_shndx == SHN_UNDEF ||

		    sym->st_shndx == SHN_ABS)

			continue;  /* skip */



		if (sym->st_shndx > SHN_LORESERVE) {

			printk(KERN_INFO "VDSO: unexpected st_shndx %x\n",

			       sym->st_shndx);

			continue;

		}



		switch(ELF_ST_TYPE(sym->st_info)) {

		case STT_OBJECT:

		case STT_FUNC:

		case STT_SECTION:

		case STT_FILE:

			sym->st_value += VDSO_HIGH_BASE;

		}

	}

}



static __init void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset)

{

	Elf32_Dyn *dyn = (void *)ehdr + offset;



	for(; dyn->d_tag != DT_NULL; dyn++)

		switch(dyn->d_tag) {

		case DT_PLTGOT:

		case DT_HASH:

		case DT_STRTAB:

		case DT_SYMTAB:

		case DT_RELA:

		case DT_INIT:

		case DT_FINI:

		case DT_REL:

		case DT_DEBUG:

		case DT_JMPREL:

		case DT_VERSYM:

		case DT_VERDEF:

		case DT_VERNEED:

		case DT_ADDRRNGLO ... DT_ADDRRNGHI:

			/* definitely pointers needing relocation */

			dyn->d_un.d_ptr += VDSO_HIGH_BASE;

			break;



		case DT_ENCODING ... OLD_DT_LOOS-1:

		case DT_LOOS ... DT_HIOS-1:

			/* Tags above DT_ENCODING are pointers if

			   they're even */

			if (dyn->d_tag >= DT_ENCODING &&

			    (dyn->d_tag & 1) == 0)

				dyn->d_un.d_ptr += VDSO_HIGH_BASE;

			break;



		case DT_VERDEFNUM:

		case DT_VERNEEDNUM:

		case DT_FLAGS_1:

		case DT_RELACOUNT:

		case DT_RELCOUNT:

		case DT_VALRNGLO ... DT_VALRNGHI:

			/* definitely not pointers */

			break;



		case OLD_DT_LOOS ... DT_LOOS-1:

		case DT_HIOS ... DT_VALRNGLO-1:

		default:

			if (dyn->d_tag > DT_ENCODING)

				printk(KERN_INFO "VDSO: unexpected DT_tag %x\n",

				       dyn->d_tag);

			break;

		}

}



static __init void relocate_vdso(Elf32_Ehdr *ehdr)

{

	Elf32_Phdr *phdr;

	Elf32_Shdr *shdr;

	int i;



	BUG_ON(memcmp(ehdr->e_ident, ELFMAG, 4) != 0 ||

	       !elf_check_arch(ehdr) ||

	       ehdr->e_type != ET_DYN);



	ehdr->e_entry += VDSO_HIGH_BASE;



	/* rebase phdrs */

	phdr = (void *)ehdr + ehdr->e_phoff;

	for (i = 0; i < ehdr->e_phnum; i++) {

		phdr[i].p_vaddr += VDSO_HIGH_BASE;



		/* relocate dynamic stuff */

		if (phdr[i].p_type == PT_DYNAMIC)

			reloc_dyn(ehdr, phdr[i].p_offset);

	}



	/* rebase sections */

	shdr = (void *)ehdr + ehdr->e_shoff;

	for(i = 0; i < ehdr->e_shnum; i++) {

		if (!(shdr[i].sh_flags & SHF_ALLOC))

			continue;



		shdr[i].sh_addr += VDSO_HIGH_BASE;



		if (shdr[i].sh_type == SHT_SYMTAB ||

		    shdr[i].sh_type == SHT_DYNSYM)

			reloc_symtab(ehdr, shdr[i].sh_offset,

				     shdr[i].sh_size);

	}

}

#else

static inline void relocate_vdso(Elf32_Ehdr *ehdr)

{

}

#endif	/* COMPAT_VDSO */



void enable_sep_cpu(void)

{

	int cpu = get_cpu();
@@ -75,6 +199,9 @@ static struct page *syscall_pages[1]; 
int __init sysenter_setup(void)

{

	void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);

	const void *vsyscall;

	size_t vsyscall_len;



	syscall_pages[0] = virt_to_page(syscall_page);



#ifdef CONFIG_COMPAT_VDSO
@@ -83,23 +210,23 @@ int __init sysenter_setup(void) 
#endif



	if (!boot_cpu_has(X86_FEATURE_SEP)) {

		memcpy(syscall_page,

		       &vsyscall_int80_start,

		       &vsyscall_int80_end - &vsyscall_int80_start);

		return 0;

		vsyscall = &vsyscall_int80_start;

		vsyscall_len = &vsyscall_int80_end - &vsyscall_int80_start;

	} else {

		vsyscall = &vsyscall_sysenter_start;

		vsyscall_len = &vsyscall_sysenter_end - &vsyscall_sysenter_start;

	}



	memcpy(syscall_page,

	       &vsyscall_sysenter_start,

	       &vsyscall_sysenter_end - &vsyscall_sysenter_start);

	memcpy(syscall_page, vsyscall, vsyscall_len);

	relocate_vdso(syscall_page);



	return 0;

}



#ifndef CONFIG_COMPAT_VDSO

/* Defined in vsyscall-sysenter.S */

extern void SYSENTER_RETURN;



#ifdef __HAVE_ARCH_GATE_AREA

/* Setup a VMA at program startup for the vsyscall page */

int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)

{
@@ -159,4 +286,17 @@ int in_gate_area_no_task(unsigned long addr) 
{

	return 0;

}

#endif
 
#else  /* !__HAVE_ARCH_GATE_AREA */

int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)

{

	/*

	 * If not creating userspace VMA, simply set vdso to point to

	 * fixmap page.

	 */

	current->mm->context.vdso = (void *)VDSO_HIGH_BASE;

	current_thread_info()->sysenter_return =

		(void *)VDSO_SYM(&SYSENTER_RETURN);



	return 0;

}

#endif	/* __HAVE_ARCH_GATE_AREA */

arch/i386/mm/pgtable.c

+0 −6
Original line number Diff line number Diff line
@@ -144,10 +144,8 @@ void set_pmd_pfn(unsigned long vaddr, unsigned long pfn, pgprot_t flags) 
}



static int fixmaps;

#ifndef CONFIG_COMPAT_VDSO

unsigned long __FIXADDR_TOP = 0xfffff000;

EXPORT_SYMBOL(__FIXADDR_TOP);

#endif



void __set_fixmap (enum fixed_addresses idx, unsigned long phys, pgprot_t flags)

{
@@ -173,12 +171,8 @@ void reserve_top_address(unsigned long reserve) 
	BUG_ON(fixmaps > 0);

	printk(KERN_INFO "Reserving virtual address space above 0x%08x\n",

	       (int)-reserve);

#ifdef CONFIG_COMPAT_VDSO

	BUG_ON(reserve != 0);

#else

	__FIXADDR_TOP = -reserve - PAGE_SIZE;

	__VMALLOC_RESERVE += reserve;

#endif

}



pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)

include/asm-i386/elf.h

+10 −18
Original line number Diff line number Diff line
@@ -133,39 +133,31 @@ extern int dump_task_extended_fpu (struct task_struct *, struct user_fxsr_struct 
#define ELF_CORE_COPY_XFPREGS(tsk, elf_xfpregs) dump_task_extended_fpu(tsk, elf_xfpregs)



#define VDSO_HIGH_BASE		(__fix_to_virt(FIX_VDSO))

#define VDSO_BASE		((unsigned long)current->mm->context.vdso)



#ifdef CONFIG_COMPAT_VDSO

# define VDSO_COMPAT_BASE	VDSO_HIGH_BASE

# define VDSO_PRELINK		VDSO_HIGH_BASE

#else

# define VDSO_COMPAT_BASE	VDSO_BASE

#define VDSO_CURRENT_BASE	((unsigned long)current->mm->context.vdso)

#define VDSO_PRELINK		0

#endif



#define VDSO_SYM(x) \

		(VDSO_COMPAT_BASE + (unsigned long)(x) - VDSO_PRELINK)

		(VDSO_CURRENT_BASE + (unsigned long)(x) - VDSO_PRELINK)



#define VDSO_HIGH_EHDR		((const struct elfhdr *) VDSO_HIGH_BASE)

#define VDSO_EHDR		((const struct elfhdr *) VDSO_COMPAT_BASE)

#define VDSO_EHDR		((const struct elfhdr *) VDSO_CURRENT_BASE)



extern void __kernel_vsyscall;



#define VDSO_ENTRY		VDSO_SYM(&__kernel_vsyscall)



#ifndef CONFIG_COMPAT_VDSO

#define ARCH_HAS_SETUP_ADDITIONAL_PAGES

struct linux_binprm;



#define ARCH_HAS_SETUP_ADDITIONAL_PAGES

extern int arch_setup_additional_pages(struct linux_binprm *bprm,

                                       int executable_stack);

#endif



extern unsigned int vdso_enabled;



#define ARCH_DLINFO							\

do if (vdso_enabled) {							\

		NEW_AUX_ENT(AT_SYSINFO,	VDSO_ENTRY);			\

		NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_COMPAT_BASE);	\

		NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_CURRENT_BASE);	\

} while (0)



#endif

include/asm-i386/fixmap.h

+2 −6
Original line number Diff line number Diff line
@@ -19,13 +19,9 @@ 
 * Leave one empty page between vmalloc'ed areas and

 * the start of the fixmap.

 */

#ifndef CONFIG_COMPAT_VDSO

extern unsigned long __FIXADDR_TOP;

#else

#define __FIXADDR_TOP  0xfffff000

#define FIXADDR_USER_START     __fix_to_virt(FIX_VDSO)

#define FIXADDR_USER_END       __fix_to_virt(FIX_VDSO - 1)

#endif



#ifndef __ASSEMBLY__

#include <linux/kernel.h>